Method And Apparatus For Protecting Downhole Components With Inert Atmosphere

ABSTRACT

Methods and systems are provided that enable the removal or reduction of moisture and any other volatile substances within downhole tools. A purging gas can be allowed to flow into the downhole tool, where it begins to interact with and dry the moisture present as well as dilute the gaseous environment therein. Then purging gas then can exit the tool, thereby removing the moisture and any other potentially polluting or corrosive gases in the tool. A vacuum pump and desiccant jar assembly also can be used to further remove moisture from the tool.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The disclosure relates generally to the field of downhole instruments. More specifically, the disclosure relates to protecting downhole electronic instruments and controls by reducing their internal atmosphere of moisture and polluting gases and filling them with inert gases.

2. Background Art

Some types of inert gas purging can be performed to protect permanent completion tools and subsea pods from moisture and polluting gases, but these tools are sealed during manufacturing. For example, reservoir monitoring tools such as those belonging to the assignee of the present disclosure have been used with a dry process for packaging downhole electronics for some time. For these conventional tools, it is essential to ensure reliable operation during five years or more, especially at the high downhole temperatures (i.e., above 100° C.). This dry process consists of vacuum burn-in, inert gas filling (with argon or dry nitrogen gas) and installing desiccants into the downhole electronics during manufacturing. However, this process is only practical for these permanent tools because it can be done during their manufacture, before they are sealed shut by welding, after which they are shipped to the wellsite and installed permanently downhole.

A similar drying process is used in the manufacture of subsea instrumentation and controls (i.e., electronics installed at the sea bed inside water proof housings or pods). One of the final steps in manufacture includes replacing the humid air inside the pod with dry nitrogen gas. However, this process is only practical during manufacture because this equipment is installed permanently at the sea bed.

A different approach is needed for moisture purging and inert gas filling of while-drilling, wireline, and other downhole tools and electronics that may be opened for maintenance, service updates and repairs in the field.

SUMMARY OF THE DISCLOSURE

In certain aspects, this disclosure can relate to inserting a purging gas into the tool, removing from the tool a gaseous mixture that includes a portion of the purging gas and undesired contents, and inserting a filling gas into to the tool.

Other aspects and advantages of the disclosure will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wellsite system in which the present disclosure can be employed, according to an example embodiment.

FIG. 2A is a diagram showing certain components of a single point purge system, according to an example embodiment.

FIG. 2B is a diagram showing certain components of a through purge, according to an example embodiment.

FIG. 2C is a diagram showing certain components of a closed loop system, according to an example embodiment.

FIG. 3A is a diagram showing certain components of a purging system including a downhole tool with an inlet port for gas, according to an example embodiment.

FIG. 3B is a diagram showing certain components of a purging system including a downhole tool with an inlet port with an interface, according to an example embodiment.

FIG. 4 is a chart that plots the inert gas bubble volume versus N2 pressure within a tool, according to an example embodiment.

DETAILED DESCRIPTION

The disclosure provides systems and methods that protect downhole electronic instruments and controls by purging their internal atmosphere of moisture and polluting gases and filling them with dry inert gas. Certain embodiments will be described below, including in the following Figures, which depict representative or illustrative embodiments of the disclosure.

FIG. 1 illustrates a wellsite system in which the present disclosure can be employed. The wellsite can be onshore or offshore. In this example system, a borehole 11 is formed in subsurface formations 106 by rotary drilling in a manner that is well known. Embodiments of the disclosure can also use directional drilling, as will be described hereinafter.

A drill string 12 is suspended within the borehole 11 and has a bottom hole assembly 100 which includes a drill bit 105 at its lower end. The surface system includes platform and derrick assembly 10 positioned over the borehole 11, the assembly 10 including a rotary table 16, Kelly 17, hook 18 and rotary swivel 19. The drill string 12 is rotated by the rotary table 16, energized by means not shown, which engages the Kelly 17 at the upper end of the drill string. The drill string 12 is suspended from a hook 18, attached to a travelling block (also not shown), through the Kelly 17 and a rotary swivel 19 which permits rotation of the drill string relative to the hook. As is well known, a top drive system could be used.

In the example of this embodiment, the surface system further includes drilling fluid or mud 26 stored in a pit 27 formed at the well site. A pump 29 delivers the drilling fluid 26 to the interior of the drill string 12 via a port in the swivel 19, causing the drilling fluid to flow downwardly through the drill string 12 as indicated by the directional arrow 8. The drilling fluid exits the drill string 12 via ports in the drill bit 105, and then circulates upwardly through the annulus region between the outside of the drill string and the wall of the borehole 11, as indicated by the directional arrows 9. In this well known manner, the drilling fluid lubricates the drill bit 105 and carries formation 106 cuttings up to the surface as it is returned to the pit 27 for recirculation.

In various embodiments, the systems and methods disclosed herein can be used with any means of conveyance known to those of ordinary skill in the art. For example, the systems and methods disclosed herein can be used with tools or other electronics conveyed by wireline, slickline, drill pipe conveyance, coiled tubing drilling, and/or a while-drilling conveyance interface. For the purpose of an example only, FIG. 1 depicts a while-drilling interface. However, systems and methods disclosed herein could apply equally to wireline or any other suitable conveyance means. The bottom hole assembly 100 of the illustrated embodiment includes a logging-while-drilling (LWD) module 120, a measuring-while-drilling (MWD) module 130, a roto-steerable system and motor, and drill bit 105.

The LWD module 120 is housed in a special type of drill collar, as is known in the art, and can contain one or a plurality of known types of logging tools (e.g., logging tool 121). It will also be understood that more than one LWD and/or MWD module can be employed, e.g. as represented at 120A. (References, throughout, to a module at the position of 120 can mean a module at the position of 120A as well.) The LWD module includes abilities for measuring, processing, and storing information, as well as for communicating with the surface equipment. In the present embodiment, the LWD module includes a nuclear magnetic resonance measuring device.

The MWD module 130 is also housed in a special type of drill collar, as is known in the art, and can contain one or more devices for measuring characteristics of the drill string and drill bit. The MWD tool further includes an apparatus (not shown) for generating electrical power to the downhole system. This may include a mud turbine generator powered by the flow of the drilling fluid, it being understood that other power and/or battery systems may be employed. In the present embodiment, the MWD module includes one or more of the following types of measuring devices: a weight-on-bit measuring device, a torque measuring device, a vibration measuring device, a shock measuring device, a stick slip measuring device, a direction measuring device, and an inclination measuring device.

FIGS. 2A-2C, discussed in more detail sequentially below, are diagrams showing example details for three of the example gas purging systems mentioned in the preceding paragraph, according to various example embodiments. Namely, FIG. 2A is a diagram showing certain components of a single point purge system 300A, according to an example embodiment. FIG. 2B is a diagram showing certain components of a through purge system 300B, according to an example embodiment. FIG. 2C is a diagram showing certain components of a closed loop system 300C, according to an example embodiment.

As shown in FIG. 2A, an example single point purge system 300A can include a gas tank 301, control box 305, downhole tool with an access port 309, and humidity sensor 313. These components can be connected to each other via various valves, pumps, pressure sensors, and the like.

The gas tank can be filled with any purging gas, such as dry nitrogen (N2) gas, an inert gas such as Argon or Helium, or an electrically insulating gas such as Sulfur Hexafluoride (SF6) in a pressurized cylinder. In various other embodiments, other types of gas or mixtures of gas such as the chemically inert noble gases, such as Neon, Krypton, or Xenon, or a relatively inert gas, such as carbon dioxide can be used. Depending on regulatory requirements and specific design considerations for the tool's thermal management, a refrigerant gas may also be used, such as 2,3,3,3-Tetrafluoropropene, or HFO-1234yf, which is a fluorinated hydrocarbon with the formula CH2=CFCF3. In certain embodiments, helium may also be used to help transfer heat for power applications; other possibilities include SF6 and CO2, particularly in high voltage applications, as helium has a relatively low dielectric strength (i.e., the maximum electric stress it can withstand without breakdown or arcing). The choice of gas can be based on the requirements and constraints of the specific application. Specifically, the purging gas or mixture of gases selected can be chemically compatible (i.e., not react chemically) with the moisture or with any of the tool's internal components, materials, or any of its out-gassing byproducts, especially over the tool's temperature range of operation and life cycle. For example, Helium is inert chemically and it can also be used to detect leaks in sealed housings. Helium may also be a choice that can help transfer heat for power applications. Additionally, in various embodiments, it may be beneficial for the purge gas to be compatible chemically, electrically, metallurgically, thermodynamically and/or physically with the tool and its constituent parts. In other words, it may be desirable for the purge gas not to arc over or embrittle any metal, swell or crack elastomers or polymers, contaminate components, or interfere with its operation or cause it to fail and/or overpressure.

With the benefit of this disclosure, those skilled in the art may appreciate the certain example advantages and disadvantages of each candidate gas and gas mixture based on chemical and electrical compatibility considerations of the purging gas with the associated electronics to be protected as well as such considerations as the gases' cost, safety, availability and environmental considerations.

In some embodiments, the gas tank can have a valve 302 that controls the release and pressure regulation of the purging gas from the gas tank. Downstream from the gas tank and valve can be a pressure reducing valve 303, and following the pressure reducing valve 303 can be a pressure sensor 304. The pressure reducing valve can regulate the pressure of the purging gas as needed, as measured by the pressure sensor. In some embodiments, it can be beneficial to use the pressure reducing valve and pressure sensor to ensure that the pressure of the purging gas is at an appropriate level. In some embodiments, an appropriate level can be between 3 and 50 psi above atmospheric pressure. The particular desired pressure may depend on a variety of factors as may be recognized by one of ordinary skill in the art having benefit of the present disclosure, such as the type and size of the downhole tool, the amount of moisture likely to be present therein, the components contained therein, the ability of those components to withstand a given pressure above atmospheric pressure without damage, cost and the pressure safety considerations of this gas purging system and its associated processes, and the like.

In an example embodiment, the control box 305 can provide a housing for the components contained therein. The control box can serve to control gas fill, dwell and purge cycles based on its sensors that measure temperature and relative humidity (or dew point temperature) of the gas, as will be discussed in more detail below. The control box can be designed and produced by those skilled in the art for operator usability in shop and field locations. To withstand rugged field use, the box can be made of appropriate materials, such as aluminum, stainless steel, polymeric or composite materials and in a form suitable to house the components and protect them during their use conditions and lifecycle environment, such as mechanical shocks and vibration, temperature range, rain, salt spray, or dust. As shown in FIG. 2A, the control box can include two solenoid valves 306, 312 (e.g., an inlet valve 306 and an outlet valve 312) and two corresponding check valves 307, 311, each used for controlling the flow of the purging gas into and out of the tool.

In one embodiment, the purging gas from the tank 301 can be permitted to flow by the operator turning the shutoff valve 302 to the ON position. Then the gas flows through the pressure reducing valve 303, enters the control box 305, flows through the inlet solenoid valve 306 and check valve 307, and then exits the control box and passes to an optional heater 308 before entering the downhole tool 121. The heater can heat the purging gas. Such heating can improve the drying and purging qualities of the purging gas, in example embodiments. Using techniques known to those skilled in the state of the art, the rate of heating can be controlled so as to minimize any risk due to excessive temperature, thermal shock or high thermal gradients within the tool. This heater can reduce the need and logistics of using large tool ovens, which may not always be accessible in the field. Alternately, the heater can be in the line from the N2 cylinder or directly on the inlet line to the tool. Other means of adding heat to the N2 or directly to the tool via the collar or chassis could be devised by anyone skilled in the art. In example embodiments, the purging gas can be heated in a variety of different ways, including for example, by having heating bands or coils disposed on or in the tool itself.

After passing through the optional heater 308, the purging gas then can enter the downhole tool 121 that is to be purged of moisture. In an example embodiment, the purging gas can enter the downhole tool via the Read Out Port (ROP) 309. In some embodiments, the downhole tool can have any number of ports (e.g., an Annular Pressure While Drilling (APWD) port 310) and any one or more of those ports can be used as an entry point for the purging gas to enter the downhole tool. Any number of gas flow ports could be designed and arranged to manipulate gas flow in selected areas. Several other logging or other tools can easily be accommodated with this disclosure, as would be recognized by one of ordinary skill in the art having benefit of the present disclosure. Optionally, any port on the tool can make use of a valve for sealing the port whenever the purging or exhaust tubes are not attached to the tool. As an example, a variation of the automobile tire valve known as a Schrader valve can be used. However, the tool valve design application can have two differences to the tire valve: 1) this valve can be within the tool; 2) this valve may not seal against the high pressure environment downhole because high pressure sealing can be made more effectively by a separate plug or plug function added to the valve.

In one embodiment, the inlet valve 306 in the control box can allow the purging gas to flow into the downhole tool via the ROP 309. This process can be thought of as the “gas fill” cycle referenced above, and this gas filling can continue until a stopping condition has been reached. For example, the flow of purging gas can continue for a given amount of time, for example 60 seconds), until a given volume of purging gas has passed into the tool (for example, depending on the volume or size of the downhole tool), or until the pressure of the purging gas in the downhole tool reaches a certain level (for example, 5 psi, as measured by pressure sensor 304.

In some embodiments, during the gas fill cycle the purging gas can start to dry the moisture present within the downhole tool, particularly where the heater was used to enhance the drying ability of the purging gas. The warm purging gas can start to mix with the water molecules and any other polluting or corrosive gases in the tool's atmosphere, causing the moisture in the tool and any polluting or volatile gases released from within its materials to diffuse and intermingle with the injected gas. Note this process is a physical mixing of gases and not a chemical reaction because the selection of purging gas was specifically made based on its compatibility with the tool, i.e., so it does not react chemically with the moisture or with any of the tool's internal components, materials, or their volatile outgases.

After the gas fill cycle ends, regardless of whether the triggering condition is based on time, pressure, volume, or any other method recognized by one of ordinary skill in the art having benefit of the present disclosure, the dwell cycle can begin. In example embodiments, the dwell cycle can constitute a period of time wherein the flow of purging gas into the downhole tool is stopped (or reduced), and the purging gas that entered the tool during the gas fill cycle remains therein and “dwells” in the tool. During the dwell cycle, the purging gas can continue to dry the downhole tool and can continue to diffuse and/or mix with any moisture, polluting or corrosive gases present therein. Those skilled in the art having benefit of the present disclosure may appreciate that this mixing can take place by a variety of well known thermodynamic, gaseous kinetic or transport processes such as: evaporation of volatile substances within the electronics or its packaging, turbulent flow whenever the purging gas flows into the tool, and, when the purging gas flow is stopped, there may be gaseous convection driven by any pressure or temperature differences, gaseous diffusion, or adsorption/desorption of gases onto, into or out of the various materials and surfaces within the tool.

In example embodiments, the dwell cycle can continue for a period of time until a stopping condition has been reached, as similarly described with reference to the gas fill cycle. The stopping condition can be based on a given time period, which can depend on a variety of factors such as the amount and/or pressure of purging gas, the size of the tool, tortuosity of the gaseous flow paths, the volume and the properties of the specific materials contained within the tool, and the like.

After the dwell cycle, the purge cycle can begin. During the purge cycle, the purging gas (along with the water molecules and any other volatile gases mixed therewith) can begin to exit the downhole tool, thereby removing moisture and gaseous pollution from the tool. In the embodiment illustrated in FIG. 2A, the purging gas can exit the downhole tool through the ROP 309. The direction and speed of gas flow can be regulated by the solenoid valves and check valves of the control box. Optionally, to regulate the exit of purging gas, an additional flow restrictor valve can be added anywhere in-line with the outlet solenoid valve 312 to the humidity sensor 313 and atmospheric exhaust 314. Specifically, in certain embodiments, during the purge cycle, the inlet solenoid valve 306 and corresponding check valve 307 can prevent purging gas from entering the ROP or returning back through the lines to the purging gas source 301 (as may have been the case during the dwell cycle), and the outlet solenoid valve 312 and corresponding check valve 311 can allow the purging gas to exit the ROP.

After the purging gas has exited the downhole tool through the outlet solenoid valve 312, the purging gas then can pass to the humidity sensor 313. In an example embodiment, the humidity sensor 313 can include an atmospheric temperature sensor and a dew point temperature sensor to measure the humidity of the purging gas. In various other embodiments, any suitable type of humidity sensor can be used to measure or estimate the humidity of the exiting purging gas.

The humidity measurement determined by the humidity sensor during successive purge cycles can indicate whether sufficient moisture has been removed from the downhole tool. For example, if during successive purge cycles, the humidity sensor reveals a relatively high to low change in the amount of humidity in the purged gas, this may indicate that an amount of moisture has been removed from the tool; conversely, a relatively low to high change in the humidity readings of successive cycles may indicate that evaporation of moisture or other volatiles is taking place, therefore moisture has not yet been removed from the tool. Finally, little or no change in the humidity readings of successive cycles may indicate that diminishing returns has been achieved for the overall purging process. Thus, monitoring the humidity reading—particularly in comparison to the reading for previous cycles—can indicate whether to continue purging the tool of moisture, or whether a sufficient amount of moisture has been removed from the tool.

After the purging gas has passed through the humidity sensor, it can be passed into the atmosphere 314. Then, as discussed in the preceding paragraph, depending on the humidity sensor reading, the entire process can be repeated to continue purging the downhole tool of moisture until a desired target value of humidity or humidity change has been achieved. For example, in one embodiment, the target value can be around 45% relative humidity. In some embodiments, the target value can be any suitable value or range.

In various embodiments for the single point purge system 300A shown in FIG. 2A, various example configurations can be used. For example, the valve on the gas tank 302, the pressure reducing valve 303, and the inlet solenoid valve 306 could theoretically be combined into one or two valves, instead of the three shown, to regulate the pressure of the purging gas exiting the tank 301 and entering the control box 305, heater 308, and downhole tool 301. Additionally, the two distinct solenoid valves (i.e., inlet 306 and outlet 312) can be replaced with one three-way solenoid valve. Such a three-way valve could include one inlet end in connection with the gas tank 301 and pressure sensor 304, one outlet end in connection with the atmosphere 314, and one end that can be switchable between an inlet and an outlet in connection with the downhole tool. Other suitable modifications, such as those that may be recognized by one of ordinary skill in the art having benefit of the present disclosure, also can be used.

FIG. 2B, above, illustrates an example through-purge system 300B that can include many of the same components as the single-point purge system 300A of FIG. 2A. As in the single-point purge system 300A, purging gas can be released from a gas tank 301, passed through pressure reducing valve 303, and pressure sensor 304, before passing through an inlet solenoid valve 306 (which may or may not be within a control box as described with reference to FIG. 2A). The purging gas then can pass through an optional heater 308 and check valve 307 (or in the opposite order) before entering the downhole tool through the ROP.

The operation of these components of the through-purge system 300B can be substantially the same or similar to those of the single-point purge system 300A, and using these components, the gas-fill and dwell cycles of the operation can be accomplished. The operation of the two example systems can differ in the purging cycle. Instead of the purging gas and moisture exiting the downhole tool through the ROP, the purging gas and moisture can exit through another port, such as the APWD. In other embodiments, one or more additional exit ports can be used.

After exiting the downhole tool, the purging gas enters a humidity sensor 313. As discussed previously with reference to the single-point purging system, the humidity sensor can be used to determine whether to continue purging moisture from the downhole tool. After exiting the humidity sensor, the purging gas can flow through an optional check valve 311, the outlet solenoid valve 312, and then into the atmosphere 314.

As shown in FIG. 2B, the purging gas after exiting the humidity sensor can flow to an optional pump 315. The pump 315 can operate to pull the purging gas out of the humidity sensor (or push the gas out of the humidity sensor), and direct it towards an additional inlet check valve 307′, where it is then passed back into the downhole tool. There are several reasons why it may be desirable to re-circulate the purging gas back to reenter the tool after passing through the humidity sensor. Namely, in situations where the humidity sensor indicates that only a small amount of moisture is present in the purging gas, it may be beneficial to pass the purging gas back into the downhole tool to further dwell and/or mix with the moisture (perhaps for a longer time) and to extract additional moisture from the tool. This may be preferable to expelling the purging gas into the atmosphere and having to use additional purging gas from the gas tank, for conservation purposes. Optionally, the purging system may be configured so that the heater 308 is in-line starting from between the junction of the two inlet check valves 307 and 307′ so that the heater's outlet connects directly to the tool's inlet port 309. By this means the purging gas may progressively warm the tool's interior to increase the evaporation of any moisture or other volatiles, which may outgas as the purging gas circulates around the loop.

In certain embodiments for the through-purge system 300B, the effect of displacement can assist in the moving of moisture or other undesired components toward the exhaust port. However, stagnant zones outside the main flow channel may behave like a single point purge where the wire channel acts as both an inlet and exhaust port. The size of these stagnant zones can be reduced by cutting additional flow channels into the chassis. In some embodiments, separate inlet and exhaust streams can be created using one-way valves along the main flow channel.

In an example embodiment for the through-purge system 300B, the three cycles (gas-fill, dwell, and purge cycles) may not be discretely separated from each other. In other words, instead of first filling the downhole tool with purging gas, then allowing the purging gas to dwell, and then finally purging the gas and moisture from the tool, the purging gas can continually or periodically flow through the tool via the ROP 309, mix with the moisture, and exit through the APWD 310. The flow rate of the purging gas may need to be adjusted accordingly to ensure that the purging gas has sufficient time in the tool to dry the tool of the moisture and successfully purge the moisture and any volatiles out gassed from within the tool.

FIG. 2C, above, illustrates an example closed loop purge system 300C. As shown in FIG. 2C, the example closed loop system 300C can include the same components present in the through purge system 300B of FIG. 2B, with an additional N2 generator 316 (or other purging gas generator) or concentrator that produces N2 at the desired flow rate and pressure, and thereby reduces the need for pressurized N2 cylinders, which can pose health and safety risks as well as unacceptable logistical costs, especially in remote field locations. The nitrogen generator 316 could also be replaced by a pump and dryer (i.e., chilled surface, membrane, or desiccant) to simply remove water vapor. The operation of the example closed loop purge system 300C can be similar or identical to the through purge system 300B of FIG. 2B, with the exception that instead of purging gas passing into the atmosphere after passing through the humidity sensor, it can pass into the N2 generator 316 where N2 purging gas is generated, and recycled into the system, whether into the inlet solenoid valve or into the heater directly. Additionally the N2 generator 316 can absorb air from the atmosphere and generate N2 purging gas therefrom.

Though the closed loop purge system 300C is shown in FIG. 2C as a modification to the through purge system 300B of FIG. 2B, it could be used as a modification to a single point purge system, such as the system 300A of FIG. 2A. In such an embodiment, the input of the N2 generator 316 could be connected to, for example, the output of the humidity sensor (whether directly or through a pump and/or solenoid valve), and the output of the N2 generator could be connected to, for example, the inlet solenoid valve or the heater.

FIGS. 3A and 3B are diagrams showing certain components of a purging system, according to an example embodiment. Certain of these components can be used in addition to or instead of the components described above with reference to FIGS. 2A-2C.

As shown in FIG. 3A, the illustrated purging system can include a downhole tool 402 that has an ROP 404 or other inlet port for gas. A vacuum hose 408 can be connected on one end to the ROP 404 and on the other end to a vacuum pump for removing moisture from the downhole tool 402. In example embodiments, a vacuum fixture can be connected to the ROP 404 for facilitating a connection between the vacuum hose 408 and the downhole tool 402. The ROP 404 in turn can be connected to a vacuum release hose, which is in turn connected to one or more desiccant jars 414 having a vent valve 416.

FIG. 3B is a diagram showing certain components of a purging system including a downhole tool 402 with an inlet port with an interface, according to an example embodiment. FIG. 3B illustrates example details for the example system shown in FIG. 3A. As shown in FIG. 3B, the ROP fixture 406 can have a valve 418 and a “quick connect” interface 420 (having corresponding male 420A and female parts 420B) for facilitating the connection and disconnection of the hoses 408, 412 and downhole tool 402.

Additionally, as shown in FIG. 3B, a vacuum pump 410 assembly can include (in addition to the pump 410 and hose 408) a female quick connect interface 420B for connecting to the male quick connect interface 420A of the ROP fixture 406, and can further include a vacuum gauge 422, a valve 418, and a trap 424. These components can be used to facilitate the pumping ability of the vacuum pump 410 and to measure the strength of the vacuum pump 410.

The embodiment of FIG. 3B additionally shows a desiccant assembly. The desiccant assembly can include—in addition to the desiccant jars 414 and valve 418 referenced above—one or more filters 426, one or more caps 428, tubing 430 or other connections between the desiccant jars 414, as well as a vent valve 416 and filter screen 432. In an example embodiment, the filters 426 can prevent the desiccants or other components from contaminating the downhole tool 402 or components thereof.

An example method for utilizing a purging system, such as the purging system shown in FIGS. 3A-3B is now described. First, example steps for attaching and using the vacuum pump 410 can include the following. In some embodiments, an example method can include attaching the appropriate adapter (depending on collar being tested) to vacuum station ROP fixture 406 and installing the fixture 406 into ROP 404 in collar. In some embodiments, an example method can include attaching the hose 408 from the vacuum pump 410 to the ROP fixture 406, opening the valve 418 on the ROP fixture 406, and turning on the vacuum pump 410. In some embodiments, the vacuum can be pulled for about 15 minutes; other suitable times are possible. In some embodiments, the valve 418 on ROP fixture 406 can be closed and the vacuum gauge 422 can be monitored for 5 minutes (during which time it may hold about 28 in Hg) without material or any leakage.

After the vacuum pump 410 is used, example steps for releasing the pump 410 and connecting the desiccant jars 414 can include disconnecting the hose 408 from the ROP fixture 406, attaching the hose 412 coming off of the desiccant jars 414 to the ROP fixture 406, open the vent valve 416 on the desiccant jars 414, and opening the valve 418 on the ROP fixture 406 (this valve 418 should be slightly opened and very slowly to regulate the release of the vacuum).

In example embodiments, the example systems, components thereof, and methods of use therefore, such as the ones of FIGS. 2A-2C and FIGS. 3A-3B can be combined with each other. For example, a purging system can include both purging gas assemblies as described in FIGS. 2A-C as well as vacuum pumps 410 and desiccant jars 414 as described in FIGS. 3A-B. This particular design combination may be advantageous for those applications where cost, availability, logistics, or safety considerations make it prohibitive to use pressurized gas cylinders or where this combination offers a desired advantage such as faster processing time or more efficient purging (i.e., to achieve a lower RH target level) than one of the embodiments described in FIGS. 2A to 2C. In contrast, this combination may be more complex, more expensive and less reliable than one of the systems described in FIGS. 2A to 2C, which may be simpler to operate or automate, less expensive and more robust because they have fewer parts, i.e., no pump 410, no desiccants, and no nitrogen generator. Each of the above embodiments of the basic methods disclosed in this patent offers advantages as well as disadvantages, depending on the specific tool 402 to be purged as well as on the user's specific requirements and constraints, which may vary depending on location, skill level, and use environment. Therefore the selection of a specific purging system design and its associated options may be made by one of ordinary skill in the art having benefit of the present disclosure.

FIG. 4 is a chart that plots 515 the inert gas bubble volume 505 (as a percentage of available free volume within the tool) versus N2 pressure (in psi) 510 within a tool, according to an example embodiment. The inert gas bubble is an imagined worst case that represents the volume the inert gas would occupy assuming there was no mixing of gasses within the tool. The model shown is based on N2 filling as an isentropic thermodynamic process (assumes ideal gas, no heat transfer and reversible process with no mixing) P1/P2=(v2/v1)̂k, where P1 and v1 are the initial pressure and volume, respectively, within the tool; P2 and v2 are the final pressure and volume, and k=1.400 for Nitrogen gas. Moreover, FIG. 4 shows that a Nitrogen filling pressure of about 50 psi would help maximize the dry air exposure within the tool before we really start getting diminishing returns of bubble volume versus applied purging pressure. This characteristic behavior is of note because it provides a basis for selecting the filling pressure design value in order to achieve efficient purging while avoiding any risk of damaging the tool's internal components by overpressure. For example, some electronic circuits, such as quartz crystal oscillators and multichip modules (MCMs), may be packaged in vacuum sealed ceramic or metal cans that can sustain only up to a limited amount of external gas pressure before failing due to deformation or collapse. The safe range of pressure and temperature for specific components may be determined by specific analysis or testing by one skilled in the art.

A dwell time between filling and exhaust allows moisture and pollution gases to diffuse and mix with the inert gas to facilitate its removal during the next exhaust cycle. This minimizes dead zones and the need for special passages and tubes to circulate gas within the tool. This makes it possible to fill and purge existing tools and a wide variety of tool architectures (i.e., tools having single or multiple ports).

In some embodiments, if tools were dry for starters, then heating dry air from 30 deg C. to 150 deg C. may bring the partial pressure within the tool from 14.7 psi to about 45 psi; however if liquid water is present (e.g., due to moisture condensation), then the pressure at 150 deg C. can be as high as about 114 psi if sufficient mass of liquid water is present. For example, if a tool's cartridge was moved from an air-conditioned room to a humid shop, moisture would condense onto the tool and be absorbed by its wiring harness, electronics and exposed parts.

If relative humidity inside the tool is about 100%, any increase in pressure may cause condensation of water vapor. Therefore, initially, the tool can be flushed with dry gas to reduce the humidity to some maximum allowable level before starting pressure cycles.

To prevent condensation, the maximum pressure applied during pressure cycles may be limited to maintain relative humidity less than 100% after compression. This pressure can increase with increasing gas temperature because generally, saturation pressure increases with temperature.

Additional details for various example embodiments exist, as may be recognized by one of ordinary skill in the art having benefit of the present disclosure. As non-exhaustive examples only, the following details of certain example embodiments are offered herein.

In some embodiments, a moisture and pollution purging process can be based on one or more pressure filling and exhaust cycles of inert gas. The warm dry gas enters via a single valve or port into the tool and circulates in and out of the tool with each cycle, thereby evaporating moisture and other volatiles inside the tool, diluting any pollution gases and exhausting it out to achieve a desired level of purity with clean dry inert gas, i.e., an acceptable low level of moisture and pollution within the protected atmosphere inside the downhole tool.

In some embodiments, a Nitrogen concentrator unit that reduces or eliminates the risks, cost and logistics of high pressure N2 cylinders can be used.

In some embodiments, the pressurized gas can be cycled in and out of the tool such that the dry inert gas is introduced relatively quickly. In such embodiments, the gas may compress and warm the internal atmosphere to help evaporate and drive out moisture, followed by a dwell time for the gases to intermix and dilute any moisture or pollution, and followed by a relatively slow exhaust to prevent any rapid cooling that could condense moisture back onto the electronics. Basically, this can take benefit from the time duration, Tpress, to pressurize the tool from atmospheric to max pressure, Pm, being less than the time duration, Tex, to depressurize, or exhaust the gas out of the tool from Pm back down to atmospheric pressure. The dwell time that may be optimal mixing or dilution of the moisture with the purging gas depends on the thermal mass and gas volume inside the tool, and the amount and type of materials that may contain volatiles and may have absorbed moisture inside the tool.

In some embodiments, an automated process can be used for purging oilfield tools with inert gas using a measurement of the moisture in the exhausted or circulated gas as a criterion for continuing or stopping the process at a given desired level of purity. In some embodiments, the purging process can be done after the electronic chassis is loaded into its collar, or housing, and sealed. This means purging can be done at any time: i.e., in manufacturing prior to shipping the tool, in a location's shop, in storage, or even on a rig prior to running down hole or immediately after the tool is retrieved uphole as a crosscheck on the quality or purity of its internal environment. In some embodiments, circulating the warm dry gas can avoid or reduce the need for vacuum prior to filling with inert gas.

In some embodiments, an instrumented setup with on-line measurement of the humidity at the exhaust or in-line with the gas circulation, such as with a Go or No-Go criterion for the internal atmosphere's purity. Pressure testing during purging can help ensure that O-rings are in place prior to running in hole.

In some embodiments, the design of a gas flow port can be made by a small plug with two O-rings and a small gas port in the middle. The plug connects to the gas filling set-up. Pulling on the plug opens the communication channel with electronics, pushing the plug back inside closes it.

In some embodiments, a desiccant bag, whether or not full of or otherwise containing moisture, can be regenerated after being baked for several hours. In some embodiments, for certain permanently installed downhole completion tools, no special attention need be paid to the desiccant bag. During manufacturing, this bag is inserted in the electronics housing and it gets regenerated during the gas filling process at the burn-in temperature (often about 150 deg C.).

In some embodiments, a relatively inert gas such as Nitrogen, Sulfur Hexafluoride, or of Helium (also can be used for leak testing the same tool), Argon or other inert gas, or mixtures thereof, can be used. Purging with inert gas pumped into the tool using pressure above atmospheric pressure can be used to reduce or eliminate the need for a vacuum pump to achieve multiple exhaust-fill cycles with the purging gas.

In some embodiments, closed loop drying by cycling the same volume of gas through a dehumidification process. The exhaust gas coming from the tool passes over a chiller to condense water vapor then the same gas can be passed through a heater before re-entering the tool to improve evaporation.

In some embodiments, pressuring the tool with dry gas can create a “bubble” (as a first approximation) within the tool of dry warm gas. For the moisture already absorbed into the electronics, local evaporation rates will vary with the material properties and the distance from the gas inlet depending on the local vapor pressure of the gas. Therefore, it is desirable to maximize the volume of dry air in each pressure cycle to enhance evaporation rates. For any given volume, FIG. 4 shows this N2 “bubble” will occupy: 19% of the total volume at 5 psi, 31% of the total volume at 10 psi, 50% of the total volume at 24 psi, 90% of the total volume at 354 psi.

In some embodiments, many of the example system and methods described herein can be used not only to reduce or remove moisture from electronic components of downhole tools, but also from mechanical or other assemblies that may contain electrical equipment. For example, motors, solenoids, actuators, relays, windings, conductors, and connections such as alternators, generators, resolvers, field coils, and the like all may contain components that can acquire moisture to be removed and/or reduced. In some embodiments, the components purged accordingly then can be filled before service with various types of gases such as inert gases, dielectric insulating gases (e.g., SF6), hydraulic oil, polymer potting, conformal coating, and/or gel.

In some embodiments, the example downhole tool system from which moisture may be removed and/or reduced can include at least one of electrical, mechanical, hydraulic, and chemical components, or some combination thereof. Moreover, although a portion of the disclosure and FIG. 1 relates to a while-drilling downhole system, in some embodiments, the downhole system can include a variety of other systems or components thereof, such as a surface connection system and associated interfaces, such as tubing hanger, subsea tree, platform tree, and surface land rig tree. As non-limiting examples only, some additional examples for applications of certain embodiments of the disclosure can include purging, removing, and/or reducing moisture from (a) hydraulic systems before filling them (or refilling them) with hydraulic oil (e.g., safety valves, isolation valves, packers, flow control valves and their hydraulic lines and connections to surface); (b) downhole electric submergible pump systems before filling them with dielectric oil; (c) downhole perforating tool's explosive charges and their associated detonators; (d) downhole chemical cutters; (e) downhole pressure balanced sensors and antennas before they are filled with dielectric oil or gel, such as in NMR, induction, resistivity, acoustic, seismic, and inductive coupling tools; and (f) other tools and/or components that may or may not be used downhole.

In some embodiments, many of the example systems and methods described herein relating to removal of moisture can be used in a variety of other applications. For example, that many of the methods and systems described herein can apply to pretreating mechanical assemblies that contain motor windings (e.g., alternators, generators, resolvers, field coils, etc.) and are then filled with hydraulic oil as opposed to gas.

Additionally, various types of moisture or other polluting or corrosive gases may able to be categorized, with different removal systems being more suited for different categories. For example, moisture that is likely to be easily removed from a tool (e.g., moisture along a flow path) may be easily and efficiently removed by a through-purge. Moisture or other gases more difficult to remove (e.g., that which “hides” in stagnant areas and adsorbed onto exposed surfaces) could make use of a an optimized purge process (such as through a single-point purge with suitable dwell time) or even by using different chassis geometry. A vacuum exhaust port also may be helpful to efficiently transport the moisture. Lastly, the most difficult moisture to remove may be that which is absorbed into hygroscopic materials and cannot be efficiently removed on a short time scale without heat. However, this moisture may evaporate slowly after purging as the boards, packages and potting seek equilibrium with the dried chassis air. This moisture can also be removed by baking (or without an oven by using our heater with two or more ports) when appropriate.

The example methods and steps described in the embodiments presented previously are illustrative, and, in some embodiments, certain steps can be performed in a different order, in parallel with one another, omitted entirely, and/or combined between different example methods, and/or certain additional steps can be performed, without departing from the scope and spirit of the disclosure. Accordingly, such embodiments are included in the disclosure described herein.

Although specific embodiments of the disclosure have been described above in detail, the description is merely for purposes of illustration. Various modifications of, and equivalent steps corresponding to, the disclosed aspects of the example embodiments, in addition to those described above, can be made by those skilled in the art without departing from the spirit and scope of the disclosure defined in the following claims, the scope of which is to be accorded the broadest interpretation so as to encompass such modifications and equivalent structure. 

What is claimed is:
 1. A method for reducing undesired contents in a tool, comprising: inserting a purging gas into the tool; removing a gaseous mixture from the tool, the gaseous mixture comprising at least a portion of the purging gas and undesired contents, the undesired contents comprising at least one of: moisture, pollution, and corrosive gasses; and inserting a filling gas into the tool.
 2. The method of claim 1, wherein the purging gas comprises at least one of: dry nitrogen gas, argon, carbon dioxide, helium, sulfur hexafluoride, and a refrigerant gas.
 3. The method of claim 1, further comprising heating the purging gas prior to removing the purging gas from the tool.
 4. The method of claim 1, further comprising: measuring at least one of a humidity and dew point of the purging gas after the purging gas has been removed from the tool; and determining whether to continue reducing moisture based on the measured humidity of the purging gas.
 5. The method of claim 1, further comprising: measuring at least one of a humidity and dew point of an internal atmosphere of the tool; and determining whether to bake the tool to reduce moisture.
 6. The method of claim 1, wherein purging gas is inserted into the tool via a first port of the tool.
 7. The method of claim 6, wherein the gaseous mixture is removed from the tool via the first port of the tool.
 8. The method of claim 6, wherein the gaseous mixture is removed from the tool via a second port of the tool while purging gas is inserted into the tool via the first port, and wherein after the gaseous mixture is removed from the tool via the second port while purging gas is inserted into the tool via the first port, the gaseous mixture is then removed from the tool via the first port while purging gas is inserted into the tool via the second port.
 9. The method of claim 1, further comprising reinserting gas removed from the tool back into the tool.
 10. The method of claim 1, wherein the filling gas and the purging gas comprise the same gas.
 11. The method of claim 1, wherein the purging gas is provided by at least one of: a gas tank and a purging gas generator that generates purging gas from an atmosphere.
 12. The method of claim 1, further comprising pumping, with a vacuum pump, the undesired contents from the downhole tool; and heating the tool to vaporize undesired contents.
 13. The method of claim 1, further comprising attaching a valve to a first port on the tool, the valve being disposed within the tool, the valve directing flow of at least one of a purging gas and a filling gas.
 14. A system for reducing moisture in a tool comprising: a source of purging gas; and a control box in fluid communication with the source for controlling a flow of the purging gas into and out of a first port on the tool.
 15. The system of claim 14, wherein the tool further comprises a second port in fluid communication with the control box.
 16. The system of claim 14, further comprising a heater for heating the purging gas, the heater receiving purging gas from the control box and heats the purging gas prior to the purging gas entering the first port.
 17. The system of claim 14, wherein the control box comprises at least one valve for directing a flow of the purging gas.
 18. The system of claim 14, further comprising a humidity sensor for receiving purging gas exiting the tool and a pump in fluid communication with the tool.
 19. The system of claim 14, wherein the tool comprises at least one of electrical, mechanical, optical, fiber-optic, hydraulic, and chemical components.
 20. The system of claim 19, wherein the mechanical components comprise at least one of motors, generators, alternators, solenoids, actuators, relays, windings, conductors, and connectors. 